1. Field of the Invention
The present invention relates to an organic electroluminescent display (OLED) device, and more particularly, to an OLED device including a heat-radiating means.
2. Discussion of the Related Art
Until a recent date, cathode ray tube (CRT) devices have been mainly used as display devices. However, recently, flat panel display devices, such as plasma display panel (PDP) devices, liquid crystal display (LCD) devices and organic electroluminescent display (OLED) devices, have been widely researched and used.
Among the flat panel display devices, organic electroluminescent display (OLED) devices have the advantages of slimness and lightweight because OLED devices are self-luminescent and do not require an additional light source differently from liquid crystal display (LCD) devices.
In addition, as compared to LCD devices, the OLED devices have excellent contrast ratios, wide viewing angles and a short response time. The OLED devices are advantageous in power consumption and are driven by low direct current (DC) voltages. Since the OLED devices solid state devices, the OLEDs sufficiently withstand external impact and have greater operational temperature ranges. Furthermore, due to their simple fabricating process, the fabrication costs of the OLED devices are low when compared with those of LCD devices.
The OLED devices are classified into a passive matrix type and an active matrix type. In the passive matrix type, scan lines and signal lines cross each other to form diodes in a matrix shape. On the other hand, in the active matrix type, a switching thin film transistor for turning on/off a pixel, a driving thin film transistor for flowing currents, and a capacitor for maintaining voltages applied to the driving thin film transistor during a frame are formed at each pixel. The passive matrix type devices have limitations on the display resolution, power consumption, lifetime, and so on, and the active matrix type devices has been researched and developed because of their low power consumption, high definition and large-sized possibility.
The OLED devices are commonly categorized as top emission-type and bottom emission-type according to a direction of the emitted light. The bottom emission-type devices have advantages in the stability and fabrication method. However, it is difficult to adopt the bottom emission-type devices into high definition products because of their restricted aperture ratio. Accordingly, the top emission-type devices have been widely used for high definition and high aperture ratio products.
FIG. 1 is a cross-sectional view illustrating an active matrix type OLED panel according to the related art. The related art OLED panel is a top emission-type.
In FIG. 1, the OLED panel 10 includes a first substrate 1 and a second substrate 2 facing the first substrate 1. The first and second substrates 1 and 2 are spaced apart from each other and are attached such that a seal pattern 20 seals edges thereof
More particularly, a driving thin film transistor DTr is formed at each pixel region P on the first substrate 1, and a connection electrode 3 is connected to the driving thin film transistor DTr.
A first electrode 5, an organic luminescent layer 7 on the first electrode 5, and a second electrode 9 on the organic luminescent layer 7 are formed on an inner surface of the second substrate 2 facing the first substrate 1. The organic luminescent layer 7 emits a predetermined color light at each pixel region P. A partition wall (not shown) may be formed between adjacent pixel regions P on the first electrode 5. When the partition wall is formed, the organic luminescent layer 7 and the second electrode 9 may be patterned and separated at each pixel region P without a patterning process.
In general, to show red, green or blue color, the organic luminescent layer 7 may include organic materials emitting red, green and blue and patterned at the pixel regions.
The first and second electrodes 5 and 9 and the organic luminescent layer 7 constitute an organic light-emitting diode E. In the OLED panel having the above mentioned structure, the first electrode 5 functions as a cathode electrode, and the second electrode 9 serves as an anode electrode.
The driving thin film transistor DTr on the first substrate 1 is electrically connected to the organic light-emitting diode E on the second substrate 2 through a connection pattern 11.
The connection pattern 11 connects the organic light-emitting diode E and the driving thin film transistor DTr across a gap between the first and second substrates 1 and 2.
Here, the second substrate 2 may be omitted to provide a flexible OLED device.
However, in the OLED panel 10, the lifespan may be rapidly decreased due to degradation of the driving thin film transistor DTr and heats generated when the OLED panel 10 is driven.
To solve the problem, various heat-radiating means have been suggested, and for example, a fan or heat pipe is added to a modularizing tool of the OLED panel. This heat-radiating means have some disadvantages. That is, the heat-radiating means has relatively weak effects for costs, and the structure and setting-up are complicated. In addition, the heat-radiating means increases the weight and thickness of the display device.